Sparking plug



. Oct. 4, 1927.

I E. J. BUCKINGHAM srmxme mus v Filed Nov. 12, 1926 v wvuymq ATTORNEY Patented Oct. 4, 1927.

UNITED STATES EDWARD JOHN BUCKINGHAM, OF CAMBERW'ELL, LONDON, ENGLANDL SPARKING PLUG.

Application filed November 12, 1926, Serial No.

This invention comprises improvements in or connected with sparking plugs and has for its particular object to avoid ClllllOLlltlGS associated with the short circuiting of the electrodes due to fouling of the spark gaps by oil, soot and other matters.

According to this invention an insulated conducting body is arranged between the electrodes so as to provide two spark gaps in series. In a practical embodiment of the invention the insulated conducting body is arranged at the lower or inner end of the socket member, shell or outer casing of a sparking plug between the said casing and a central insulated electrode and so arranged that, in the event of a short circuit of the central electrode to the insulated conducting body or of the said body to the outer casing of the plug, a spark gap is provided between the said conducting body and the outer casing or between the central electrode and the said body as the case may be. Pref erably a single conducting body is used in the form of a ring mounted within the inner or bottom end part of the plug casing with the interposition of a ring of insulation, and, to facilitate assembly of the insulation and ring and to prevent them from falling out of position, they are of tapered form to fit within a tapered seating in'the plug casing.

The accompanying drawing shows in central section a sparking plug made in accordance with this invention.

In carrying out the invention, according to one practical example, the outenmetal casing a of the sparking plug, which as usual has a screwed plug part b at its lower end for screwing into a. cylinder, is formed within the screwed plug part b with a downwardly tapered seating .11. The taper may, if

desired, extend upwardly within the body of the casing for the seating of a layer of insulation (Z, and apart from improvements according to this invention the plug carries a central insulated electrode 0 with one or more sparking points.

The said tapered seating within the screw plug part of the plug casing supports a conducting ring 7 in the form of a hollow frustum of a cone, a ring or layer of the insulating material cl, for example mica, being interposed between the ring f and the tapered seating.

The upper end of the ring f is of such a 148,028, and in Great Britain November 2, 1925 diameter that it cannotfall through the insulation lined seating, and the dimensions of the ring are such that, when said ring is mounted in position by driving it in from above, its lower end projects slightly beyond the lower end of the screwed socket part of the plug casing. The insulation d may also extend slightly beyond the lower end of the plug casing a but not to the same extent as the ring. The outer end 9 of the ring can be slightly expanded to prevent the ring from being moved back into the plug casing.

Under normal conditions sparking will take place between the electrode 6 and the grounded outer casing 64 in the usual manner because the ring j" is insulated. In the event, however, of an accumulation in the spark gap of soot or other matter, this latter will invariably be lodged on the ring 7 due to the projection of said ring beyond the lower end of the plug casing and thus current will be conducted to the said ring and sparking will take place between the latter and the lower end of the plug casing. Even if soot or other matter may have bridged the gap between the ring and the plug casing there will inevitably be some points not bridged so that sparking, may take place until such time as the plug can be removed and cleaned.

I claim:

l. A sparking plug comprising an open ended plug casing having a conical bore diminishing towards the outer end thereof, a conical ring fitted into the said bore to project slightly therefrom, the said ring being retained in place by expanding its outer edge, a layer of insulating material interposed between the casing and ring, and an electrode carried by an insulating support in the said plug so as to have its terminal end within the space within the said ring.

2. A sparking plug comprising an open ended plug casing having a conical bore diminishing in diameter towards the open end thereof, a conical metallic ring fitted into said bore to project slightly therefrom,

a layer of insulating material interposed between the casing and the ring, and an electrode carried by an insulating support so as to have its terminal end in the space within the ring. a

EDWARD JOHN- BUOKINGHAM. 

